This disclosure is directed to light emitting diode (LED) devices and materials for LED device components, and in particular to LED lighting devices comprising polycarbonates.
LEDs are semiconductor devices that emit incoherent narrow-spectrum light when electrically biased in the forward direction of their p-n junctions (boundary between P-type and N-type semiconductor), and are thus referred to as solid-state lighting devices.
LEDs can be used in applications as diverse as aviation lighting, automotive lighting, advertising, indoor lighting and traffic signals. Recently, with the development of LED technology, LEDs are fast replacing incandescent and fluorescent lighting. Compared to other lighting devices, LED products offer longer life span and higher efficiency.
The lifetime of LED products can be from 25,000 to 100,000 hours. However, heat can shorten this time significantly. With the development of high-power LED chips, the LED devices are subject to higher junction temperatures. This causes stress on the material for LED components, which may lead to early failure of the devices. The most common symptom of LED failure is the gradual lowering of light output and loss of efficiency due to the yellowing of LED housing materials. Sudden failures, although rare, can occur as well. Thus, LED lighting devices having higher light output and less yellowing components over its lifetime are continually sought.